Open with the problem you are solving, not a list of screens. What kind of user will use this, with what frequency, and what happens today? A vendor who understands the goal often proposes a simpler way to reach it; someone handed only a list of screens can only price the list as written.
Define what is included as concrete flows: who does what, and what happens next. Equally important, write down what is out of scope. A written out-of-scope list saves more friction during acceptance than almost anything else in the document. Mark too which items are decided and which are still open — estimators price uncertainty, and pretending everything is fixed helps nobody.
Write down the hard constraints. This means existing systems the crypto igaming software development has to talk to, the data you already hold and its condition, security and compliance rules, user volumes, which devices matter and any technology you are committed to. If there is a hard date, explain what drives it: a good team will often resequence the work how to find right software development company meet it, flutter developer hourly rate but not if the date is a secret.
Define what completion means for the important items. Testable acceptance criteria do not need special syntax: a plain-language note describing the expected behaviour is sufficient. This one section shortens the review at the end by a surprising margin and closes off the usual argument at handover.
To close, ask for a specific format. Ask for an itemised estimate, the assumptions used, whatever the dedicated team vs outsourcing considers risky and an optimistic and a pessimistic figure. Treat a wide range as information, not evasion: it usually points to exactly which requirement is unclear. At that point rewrite that part and request a revised number — the second estimate will be much more reliable.
